Patent GB-662036-A (GB)
Title: Improvements in or relating to electric switches
IPC: H01H9/06
Filed: 1949-10-28
Abstract: 662,036. Retractive switches; tumbler switches. IGRANIC ELECTRIC CO., Ltd. Oct. 28, 1949. [Oct. 29, 1948] No. 27706/49. Class 38 (v). An insulating switch base 15 suitable for use in conjunction with trigger-operated mechanism and for mounting in a tool-handle, has three recesses 16, 17, 18, Fig. 4, of which 16, 18 accommodate a pair of fixed contacts 19 and a movable U-shaped bridging contactor 20. Rivets 22 secure the contacts 19 and connect them to terminals 32 also secured thereby on the respective corners 28-31 of the base. Each corner, as 28, has parallel surfaces 28a, 28c, joined by a sloping surface 28b, the surfaces 28b, 28c having recesses 28e, 28f, respectively formed therein to house a terminal binding screw 39 and a reduced rectangular fixing- terminal-extension 32a, Figs. 3, 3a. The contactors 20 are pressed by springs 21 against an insulating plate 23 slidable in notches 24, 25, which interconnect the recesses 16, 17 and 17, 18 respectively. A cam operating member 26 overlying the plate 23 is of strip form and has a T-shaped end 26a located in a corresponding portion 17a of the recess 17, the bottom of the portion 17a being sloping and the member 26 being retained therein for pivotal movement by a rubber diaphragm 27 which overlies the top of the base to afford a dusttight enclosure. The free end of the cam 26 comprises mutually inclined portions 26b, 26c, 26d, the portion 26b extending through an opening in the diaphragm 27 and the portions 26c, 26d, co-operating with a sheet metal actuating member 47 which is reciprocably mounted in the inverted channel-section of a combined cover and frame member 38, Fig. 2. A stiff fibre plate 44 and flexible fibre member 45 are interposed between the cover 38 and diaphragm 27, the assembly being secured by rivets 41, and the member 45 may extend around the sides of the base to form an envelope insulating the terminals 32. The reciprocable actuator 47 has a slot 47b, for clearing a rivet 41 and an off-set extension 47e carrying a bush 48 and parallel to a similar extension 38c of the cover 38. The extension 38c has an offset portion 38e carrying a bush 51 pivotally bearing a pin 50 joining the two sides 49a, 49b, of a U-shaped section finger-operated trigger 49 biassed in the clockwise direction by a spring 46. A further pin 52 joining the sides 49a, 49b, extends through the bush 48 with lost motion clearance. Normally, the actuator 47 is moved to the left by the spring 46 acting through the pin 52 to engage the surface 26c of the member 26, which in turn acts through the plate 23 to hold the contactors 20 open. On depression of the trigger 49, pin 52 engages the bush 48 moving the actuator 47 to the right which then engages the cam surface 26d and the contactor springs 21 take up the lost-motion between the pin 52 and the bush 48 moving the actuator 47 further to the right to give an audible and tactually perceptible signal to the operator. In this embodiment, an additional wire anchoring lug 33 having binding screws 35, 36, is provided beneath the switch base, the lug having no electrical connection with the other switch parts. In a modified construction, Fig. 7, in which the switch may be latched closed, the coverframe 56 has an offset extension 56d carrying a post 61 and a pivot 73 for the trigger 68, and an offset extension 62c of the reciprocable actuator 62 supports a post 67, slots 63, 66, being provided in the actuator 62 to permit its 'movement. The side 68a of the trigger 68 has a notch 69 providing extensions 68f, 68g which co-operate with the post 67, and a bracket 68h on the other side of the trigger slidably supports in conjunction with the trigger finger surface 68c, a latch button 70 which is retained against the pressure of a spring 72 by a washer 71 rivetted thereto. If the button 70 is not used, this embodiment functions similarly to that previously described by the lost-motion connection 'between the extensions 68f, 68g, and the post 67. If the trigger 68 is moved counter-clockwise more than is necessary to operate the switch and the button 70 depressed, on release of the trigger 68 the shank 70b of the button and the washer 71 engages the post 61 and the switch is latched closed, release of the latch 70 being effected by slightly depressing the trigger. The switch base and associated parts may be incorporated in a tumbler switch, Fig. 9, in which a dolly 80 operates the cam member 26, the switch being mounted by holes in a bracket 82. In Fig. 10 (not shown), the tumbler switch is mounted by an externally threaded bush in which the dolly is pivoted. U.S.A. Specifications 1,889,259, 1,977,078, 2,089,032 and 2,295,668, are referred to in the Specification as open to inspection under Sect. 91.